Marked steel bar and method of marking



Aug. 2l, 19,45;

c. v., scHuYLER MARKED STE'EL BAR AND METHOD OF MARKING Filed Jan. l0,1944 IN Vgn TOR Char/e5 l( LSC/7 ,4 TTORN E Ys.

Patented Aug. 2l, 11945 uNiTaD PATENT y MARKED swam. ma um Marilou 20F`ciau-ies v. Schuyler, Philadelphia., ris.

Application Jennery 51o, '1e-944, semi Nq. 517,760

rcisims. cores-iis) viously, Vthe extra labor represented `by this lat-This inventionprelates .to marking steel bars.

As steel `laars or rodsiare customarily furnished i to processors of thebars or rods", :suchas ftool and` die makers,` fabricators, the metalmanufacturing industry or processors lof steel 4from` bar stocks orshapes Vinto iinished machinery or metal working parts, `or,`metaljfarticles, as, for purely illustrative purposes, -todie}or toolmakers, for example, they are furnished -in rather exact sizes in theparticular snapes required, and

in an annealed or relatively` soft condition. l The bars underdiscussion maybe of any `desired e profile in' section, generallycharacterlzedias steel bars, hats, squares, rounds, shapes. etc., .butfor purposes of illustration only will be assumedherem to be oblong barssubstantially square ,incross section. V l,

It is conventional forthe-customersprocessors, or users to processtherelativelyy softlbarsorrous to exact shapes, as by machining one,two, .or more sidesor `lateral surfaces of the rodsfto exactmeasurements to secure exact thicknesses. Such accurate machining ispreliminary Ato 'hardening operations either inthe l plant oftheprocessors, or in special heat-treating plants operated :by others. v`ve 4 It will be evident that for suchpurposesias dies ,ter .procedurerepresents a direct `loss to the processor.` Y llt V:is an unfortuitousfactthat .bars as formed fandrolled in the fabricating millareinvariablvsubject to what might beidesignated as differen- ,tial carburizing`.whereby `through partial car.- fburizmg `ordec-arourizing :there isroi-med onthe lateialsurfaces or' the finished `barsto be delivered tothe customers, `an undesired superficial' skin or layer. ThisAoutersurface which is called fsoft skinfor "mill skin is `integral withYthe body of Athe steel bar, `mit is `different from the ,mass of theoarinsicieor .the skin Aprobably both chemically and molecularly. Themill skin, as n; ywillbe designated hereinaiter for simplicity, reactsdifferently -to :the Yhardening heat-treatment ultimately `given to thebar after machining processing so Althat unless it lis removed beforesuch .hardening heat treatment. such skin remains ,relatively soft `andif `it. happens Ato be a working surface, `ruins tne piece upon whichitappears. As ,inmany uses :for bars or on many nnlshedoriunnishedsurfaces ofbars, its presf and tools, again for purely illustrativeexample only, the finished Vheat-treated and hardened surfaces must 'beof uniform density andhardnessand must also be ofeXtremeaccuracy/ofdimensions. Any deviation from exactness ofdlmensionimmediately lconverts the har` thus worked upon into scrap, atleast asfar as'the particular purposeintended for that speciilcbar is concerned.On the other handfany incidental happening that makes one of the workingsurfaces of a tool softer than another inthe nished tool or die, forexample,. even whilefex'actand accurate dimensions aremaintainedisacircumf" "stance which also converts thetooljor `die intoscrap,` at least so far as concerned. Y s

All tool anddie makersandthe like following conventional prior artpractices are subject to very appreciable losses through theseiactors,`:as

the instant purpose is the time wasted in unusablemachiningand-heattreating operations is quite appreciable ,apart fromthe diiference in value of new rolled bars and that of scrap metal.

Of course, when"scrap is mentionedfhereinI it is intended to-besumciently genericas-lto `inence is not vnecessarily undesirable andithe expense' of removal `would be high, it is normally `never removedVby Vthe mill, land therefore `conventionally always'appearsion barssoldto consumers. but its k.untoward `effects `are vknown throughLeiiperiencetto `alrnost all heat-heaters, and l:by Vmany a of fthemechanics `,who must work Atliexn'etalpreparatory toheat treatment.Knowledge of 4its existence, however, is not enough, :as among other'`disadvantages of .the millskin is vthefactthat itcannot ,readilybedetected visueally. `In-otherwordspif lpartially.removedfhy .a l

machining'soperation, *,the remaining layer of mill skin visuallyisidenticalwiththe massi' `real steel Lbeneath the-surface `or `on,an'adjoin@ ing surface' from -which' all of the Vmill Y skinfhas beenremoved:` LMoreover, the depth or thick- ,ness of the 4.mill skin cannot`be `exactly ,predetermined. AIn ,otherwworda it may vary lin 4depth`within quite wideY :limits `between two 'lots or batches1of i bars l:of`the same rolled sizes but of.,different frunsi As .the Aexistence of`the :mill skin Vfis visually diiiicult `to `ascertain, i and as thethickness varies "slightly :between bars, `.its

' L exact i removal is ltechnically a diicult matter.. 50`

Among 'the difficulties attendant'upon use ot' i steel possessed of.mill skin, lis A,thepfact `that `in Y .machinirlg two opposite sides ofa substanclude both actual andeiective scrap. That is,

it includes both barsV that areactually wasted for all purposesotherthan re-'melting in new steels or similar scrap uses, as Awell ,as4those whch'may be susceptible to salvage4 by further machining andhardening processes to form nn' ished bars of smaller `dimensions -thancontemplated in the initial machining operations; Ob-

`tia'lly i square :in section, for, instance, `it ,is not`uncommon.gforthemachinist to removetoo much -skin fon one surface,`anclpmeasuring the-second cut accurately with reference, toftheflrst`with a micrometerin orderv toihavea finishedi piece. ot' exactjthickness, 'he i may remove *,too little onthe second surface with -aconsequent 1 retention i on 60 ithe supposedly `accurately finishedsurface `of a vention, indicating in dotted lines the and undue amountsof scrap.

It is readily possible for the fabricating or roll-A ing mill todetermine rather accurately what the thickness of the mill skin is forany run or lot of bars in a given output. Usually the depth of mill skinis substantially the same for all pieces in a given run.

It is among the objects of this invention:. to provide a marking systemfor steel bars by which the fact that a given .surface is formed of millskin can be readily detected visually; to provide a system of markingfor steel bars by which the depth of the millskin on the surfaces of thebars can be readily determined; to provide a method of marking by whichthe fact of the existence of mill skin on a surface and its depth canboth be determined and continuously indicated; to provide a new articleof manufacture comprising a steel bar with markings of the existence anddepth of superficial mill skinV on the bars; to furnisha gauge for theremoval of the superficial mill skin on a bar; to provide 'a two-stageprocess for hardening steel bars without also attempting unwittinghardening of the supercial mill skin inadvertently therewith; and manyother objects and advantages of the invention will become more apparentas the description proceeds.

In the accompanying drawing forming part of this description,

Fig. 1 represents an end elevation of a steel bar according to anillustrative form ofthe indepth of the mill skinv with which the bar iscompleted, and illustrating the grooves or channels by which both theexistence and depth gauging of the mill skin is indicated. o

Fig, 2 represents a perspective of a. bar according to the preferredform of the invention, with an vend, reduced in thicknesson `twoparallel sides to the desired finished thickness, and indicating indotted lines the thickness of the iat is removed in the processing. 1

Fig. 3 represents a similar view of another steel bar marked accordingto the preferred formV of the invention, with all four of the sidesurfaces Fig. 1, indicated by dotted unes ls, will facilitate anunderstanding of the problem involved in' forming a tool in which onepair of opposite parallel surfaces, for instance, isto be machined orground off to establish a certain exact distance between the parallelmachined surface. If, as is the normal case. the distance betweensurfaces li and I2 after they have been accurately machined is to bejust exactly the vertical distance between the dotted lines I adjacentto surfaces l and i2 indicating the termination of the mill skin `andthe beginning of the steel mass, the machining must be most accuratelyaccomplished. If the cut on surface Il, 'forlinstance, should be toodeep, it will be clear that the accurately measured machining of thesurface i2, measured relative to the previously machined surface il,will be too light, and the cut will come between the outer surface i2and the dotted line I9 adiacent thereto, and there will consequently bea thin residual layer of mill skin on the surface I2. On the other hand,if' the cut on surface Il l is too light, then on surface l2 it will betoo In this latter case it will then be the il that will still retainpractices, there is no way of preventing such occurrences, and it islargely a matter of experi-v ence as to average depth of mill skinwhether all is removed that is intended to be removed or only a part.

In carrying out the instant invention in a purely illustrative manner, Iprovide in all ofy the surfaces slots or grooves, respectively I1, I8..

20 and 2l, which I prefer to designatey as surfacepiercing apertures orrecesses, preferably extending full length of the bars, and eachaperture of a depth exactly corresponding to the depth or thicknessofthe mill skin on the surface containing the particular aperture. The-grooves are quite narrow, if desired, and may comprise saw cuts,milling machine grooves, drilled recesses, or

otherwise, so long as they are both visually noticeable in the externalsurface, and of sum'- cient Vwidth at their bases at themergence of themill skin and the real steel as to be visually min skin toward the endreduced in thickness by removal Vor the soft skin on eachsurface.

Fig. i represents a side elevation of the-bar of Fig. 2, and

Figs. 5 and 5 represent end elevations of modinedV forms of bar to whichthe invention pertaires.

l of the bar is, at the surfaces just recited, completed by a continuoussuperficial partially carburized or decarburized mill skin IEv definedby dotted lines i9 as shown. The possibly slightly exaggerated depth ofthe mill skin according to The central portion or4 the mass onoticeable, as any metal above the bottoms -or bases ofv the aperturesis removed.

Usually, after determination of the average depth of themill skin fromYthe ilrst bar or rod, or so, the experienced rolling mill employeeswill, for example, setcooperating saws, such as rotary saws at theproper clearance for given thicknesses of bars as to make cuts of theproper depth for the given thickness or depth of the .mill skin on thebar, and then will rapidly feed the entire lot of bars in successionthrough the saws to impart the desired depth of aperture cut to eachsurface. The'apertures disclosed, whether continuous, or intermittentand longitudinally spaced, or evenA annular, will continuously indicatethe existence of mill skin on the given surface Yof the bar underconsideration to all concerned, whether it be the machinist or theheattreater, and, of probably equal importance, it

will also continuously indicate the depth Yof the by the substantialrectangle 22 defined by the dotted and full lines of Fig. 2, which alsoremoves the boundary surfaces defining the groove I1 at said end of thebar, so that thelower surface of the aperture Il is exactlytangential'to the plane of the machined surface 23, which thus bothobliterates the guide and gauge groove, and also simultaneously removesjust the right amount of the outer mill skin surface as to expose thesolid steel surface 23 of the mass I5 of the bar I0. Obviously. theremoval of the exact amount of steel comprising the mill skin has alsocompletely removed the guideand indieating aperture I'I with it. It willbe apparent at this juncture therefore that anyone knowing thesignificance cf the surface apertures will be able to look at the bar,with its one surface (I I) machined in part only (at 23) which, ofcourse, can be for the full length of the bar I0, if desired, and cantell that there are three other surfaces which still retain mill skin,and one surface containing, in part at least, no mill skin. If al1 fourare Working surfaces, they cannot properly be heat treated to make asatisfactory tool. It also advises the machinist of the condition of theremaining surfaces on the bar, that is, whether the mill skin is stillto be` removed, and to what extent. Pursuant to the just describednishing of the first surface to the desired length according to the useof the ultimate tool or die and to at least the required depth of millskin removal according to the predetermination accorded by the depth ofthe channel or groove I1, then the corresponding parallel surface I2 issimilarly machined. In this operation, the groove aperture in surface I2is used as the gauge to insure the removal of the proper depthofdifferentially carburized mill skin until the groove 20 has but justbeen obliterated. This will thus give a finished parallel surface 24 ofthe desired length longitudinally of the bar, and

` with both the surfaces 23 and 24 formed of pure uncoated steel withoutmill skin on either surface. If these two surfaces alone are all that4may be desired to be hardened, after determination of the exactdimensions between the surfaces has been established, by such subsequentmachining or grinding steps as may be necessary to attain the propermicrometer reading for the thickness of the tool desired, the bar isgiven to the heat-treater for hardening. The latter knows at once bymere visual inspection that the two side surfaces I3 and I4 stillcontain mill or soft skin, and that no such skin remains on eithersurface 23 or 24, and can proceed accordingly to heat-treat the bar,knowing that the work cannot be rejected on the ground that either ofthe surfaces 23 or 24 still contain rudimentary or residual mill skinlayers.

If it is desired that the entire end, or indeed, the entire bar besusceptible to proper heat treatment to establish uniform hardness, thenthe bar as machined in Fig. 2, may be completed bythe formation of theconnecting side surfaces 25 and 26, formed by suitably removing the softskin layer on the sidesY I3 and I4 until the gauge grooves 2| and I8respectively have but just been removed. The reduced end of the machinedbar of Fig. 3 formed of surfaces 23, 24, 25, and 26 will be immediatelyunderstood by all concerned to have no mill skin remaining and thereforthat A al1 four surfaces can be evenly hardened.

As shown in Figs. 5 and 6, the invention is applicable to bars ofdifferent contours from v It willalso be clear that the skin-indicatingand depth-` the illustrative preferred embodiment.

defining surface-piercing recesses or apertures may be of any desiredshapes and sizes, and, as noted,`may be continuous or interrupted, maybe annular as well as elongated, and may be provided by punches or thelike as well as by the actual removal of metal. It will be evident thatthe only essential is that the mark be in the surface of the bar, andthat the mark have a metal-piercing depth equivalent to the: thicknessof the mill skin and belof observable width at its base. l

' I'he advantages of the invention are thought to be obvious, aswill bethe fact that the descrip,-

tion as to marking above given is not limitative, either as to time orpersonnel, as the marking does not need to be done at the fabricatingmill to the marking operations as the steel in the rolling mill. Indeed,the only requirement is that it be properly marked before the nalmachining or grinding and hardening operations are begun.

Having thus described my invention, I claim: l. The method of formingbar surfaces of metal bar stock as a preliminary to heat treatment whichconsists in ascertaining the depth of mill skin on the surface of thebar, forming `a surfacepiercing aperture in the surface of the depth ofthe mill skin, removing an area of the surface layer of mill skin untilthe part of the aperture in said area has been removed to insure removalof all of the mill skin in said area of the surface.

2. As an article of manufacture, a steel bar stock having a surfacelayerformed of mill skin, asurface-piercing aperture disposed in andextending completely through the mill skin layer only as a visualindication of the existence of the mill skin and as a depth gauge of thethickness of the layer of mill skin.

3. As an article of manufacture, a steel bar stock having a surfacelayer formed of mill skin,

mill skin onlyon said surface as visual indica-` tions of the existenceof mill skin' on a given surface containing an aperture and as a gauge`of the thickness of such layer of mill skin, each surface-piercingaperture comprising a machined `surface groove of uniform size extendinglongitudinally of the bar in each respective surface.

CHARLES v. scHUYmR.

